The invention relates generally to a system, apparatus and method for harvesting energy, and more particularly to an energy harvesting system, apparatus and method for harvesting acoustic energy and converting it into electrical energy for running a sensing assembly.
The U.S. Congress promulgated the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act in 2000. The TREAD Act provides that by the year 2007, all new motorized vehicles operated on the U.S. transportation system must include a tire pressure sensing system to monitor for and report the occurrence of unsafe tire pressure. The TREAD Act is applicable to all consumer and commercial trucks and automobiles.
The tire pressure sensing system is to include a tire pressure sensor mounted in a position suitable for determining the tire pressure, such as, for example, on a wheel rim within each tire. Current power sources for sensors include batteries and RF sources. The use of batteries in some applications has disadvantages. Batteries are not environmentally friendly, amounting to millions of discarded batteries per year. For applications where replacement of the battery is problematic, the only battery option is a lithium ion battery (Li/CFx), which is expensive. Further, batteries are subject to a loss in capacity at certain temperatures, such as at minus 40° C. Further, many batteries have a large enough size and mass to render them impracticable for certain applications.
There exists a need for an applicable power source capable of providing power to sensors in small or crowded environments. For example, there exists a need for a power source for the required tire sensors. The power source must have a small enough profile to fit within wheel rims. Further, the power source should be renewable or, at the very least, have a long lifetime to lessen the need for replacement.